Method and apparatus for retaining a fusion member while delivering the fusion member between two vertebral bodies

ABSTRACT

Some embodiments of the invention provide an apparatus that (1) delivers a fusion member between two vertebral bodies after at least a portion of the fibrocartilaginous disc between the vertebral bodies has been removed, and (2) affixes the fusion member to the vertebral bodies. In some embodiments, the apparatus includes (1) a fusion member that is delivered and positioned between the vertebral bodies, (2) a delivery mechanism that delivers and positions the fusion member between the vertebral bodies, and (3) an anchoring member that affixes the fusion member to the vertebral bodies.

CLAIM OF BENEFIT TO PRIOR APPLICATIONS

This application claims benefit to U.S. Provisional Patent Application61/211,484, filed on Mar. 27, 2009. This application is a continuationapplication of U.S. patent application Ser. No. 12/383,950, filed Mar.27, 2009, now U.S. Pat. No. 8,382,839. This application is also acontinuation-in-part application of U.S. patent application Ser. No.12/113,362, filed on May 1, 2008, now U.S. Pat. No. 8,313,528. U.S.patent application Ser. No. 12/383,950 claims benefit to U.S.Provisional Patent Application 61/040,136, filed on Mar. 27, 2008; U.S.Provisional Patent Application 61/109,175, filed Oct. 28, 2008; and U.S.Provisional Patent Application 61/148,036, filed Jan. 28, 2009. U.S.patent application Ser. No. 12/113,362 claims benefit to U.S.Provisional Patent Application 61/040,136, filed Mar. 27, 2008. Theabove-mentioned applications, namely U.S. patent application Ser. No.12/383,950, now issued as U.S. Pat. No. 8,382,839 and U.S. patentapplication Ser. No. 12/113,362, now issued as U.S. Pat. No. 8,313,528,and U.S. Provisional Patent Applications 61/211,484, 61/040,136,61/109,175, and 61/148,036, are incorporated herein by reference.

FIELD OF THE INVENTION

The invention pertains to spinal implants and surgical procedures forspinal fusion and stabilization.

BACKGROUND OF THE INVENTION

Back and neck pain are the leading causes of disability and lostproductivity for American workers under the age of 45. Degenerative discdisease and its sequelae, whereby the fibrocartilaginous disc betweenadjacent vertebral bodies loses height, hydration and structuralintegrity, is one of the most common causes of back and neck pain andmay develop secondary to traumatic injuries, inflammatory processes orvarious degenerative disorders. When conservative treatment fails,surgical fusion of the vertebral segments across the abnormal disc maybe the only currently available procedure for pain relief. An increasingnumber of these spinal fusions are performed each year. It is estimatedthat over half a million of these procedures were performed in theUnited States last year alone.

Various surgical approaches to abnormal lumbar disc spaces are employedand include anterior interbody fusions, posterior interbody fusions andtranforaminal fusions. At cervical levels, an anterior approach is oftenemployed. These procedures may be augmented by various posterior elementinstrumentation techniques. Regardless of the surgical approach, thegoal is to achieve solid bony fusion between the involved endplates andeliminate the symptoms caused by motion and associated degenerative andother reactive changes between these unstable vertebral segments.

The first lumbar fusion procedures involved removal of a portion of theabnormal disc and placement of autologous bone graft material in thedisc space without other instrumentation in the vertebral bodies orposterior elements. This approach often failed due to inadequatestructural integrity. Subsequently, cortical bone dowels and femoralring allografts were employed in an attempt to restore disc space heightand augment structural integrity. After U.S. Pat. No. 4,961,740 (“Ray,et al.”) introduced the concept of the threaded cylindrical interbodyfusion cage in 1990, numerous other interbody fusion devices weredeveloped. These devices include cylindrical, rectangular, and taperedcages and spacers composed of metals, polymers, human bone allograft andother materials. Some of these devices incorporate or are coated withhuman bone morphogenetic protein or other agents to promote new boneformation and accelerate fusion. Despite these advancements, failurerates for spinal fusion surgeries remain unacceptably high, greater than10 percent in most series.

Therefore, there is a need in the art for an improved method to effect amore rapid, reliable fusion between unstable vertebral segments andavoid the considerable medical and economic impact of failed spinalfusions.

SUMMARY OF THE INVENTION

Some embodiments of the invention provide an apparatus that (1) deliversa fusion member between two vertebral bodies after at least a portion ofthe fibrocartilaginous disc between the vertebral bodies has beenremoved, and (2) affixes the fusion member to the vertebral bodies. Insome embodiments, the apparatus includes (1) a fusion member that isdelivered and positioned between the vertebral bodies, (2) a deliverymechanism that delivers and positions the fusion member between thevertebral bodies, and (3) an anchoring member that affixes the fusionmember to the vertebral bodies.

In some embodiments, the interbody fusion member is a shaped block(e.g., a rectangular or oblong block) with one or more channels (e.g.,tubular channels). As mentioned above, this member is placed betweenendplates of adjacent vertebrae following a partial or completediscectomy. In this position, two or more sides of the fusion member arein contact with the opposed endplates. These contacting sides in someembodiments restore both disc height and physiologic lordosis. In someembodiments, these sides are parallel to each other, whereas in otherembodiments, these sides are nonparallel such that the fusion memberpresents a tapered profile when viewed laterally. In this position, oneor more anchoring members (e.g., one or more open-tipped or close-tippedneedles) can be pushed through the one or more channels of the fusionmember and into the marrow space of one or more of the vertebral bodies,in order to affix the fusion member to the vertebral bodies. This isfurther described below.

In some embodiments, the delivery mechanism that delivers the fusionmember between vertebral bodies includes (1) a delivery housing thathouses the anchoring mechanism and (2) a retention mechanism thatcouples the delivery housing to the fusion member. The delivery housingof some embodiments includes channels that run the entire length of thedelivery housing that guide the anchoring mechanism to the properchannel opening of the fusion member. In some embodiments, the deliveryhousing also includes channels that guide retention rods toward theretention mechanism of some embodiments.

In some embodiments, the retention rods have retention teeth that matewith retention grooves on the fusion member. The retention rods,grooves, and teeth form the retention mechanism of some embodiments.Other embodiments might have different retention mechanisms. Forinstance, in some embodiments, the retention teeth are on the fusionmember while the retention grooves are on the retention rod. Moreover,instead of, or in conjunction with, this tooth and groove approach, oneof ordinary skill will realize that other embodiments use otherretention structures (e.g., other male/female structures, otherstructures such as expandable clasps that encapsulate the lateral edgesof the fusion member, other structures such as a clamp, etc.) to affixthe delivery mechanism to the fusion member.

The retention mechanism is used in some embodiments as a way ofcontrollably detaching the delivery mechanism from the fusion memberafter the medical practitioner (1) determines that the fusion member isplaced at the desired position between two vertebral bodies, and (2)inserts the anchoring members into the vertebral bodies in order toaffix the fusion member to the vertebral bodies. When the medicalpractitioner determines (e.g., by viewing x-ray images of the patient)that the fusion member is not placed at an appropriate position betweentwo vertebral bodies, the medical practitioner can use the deliverymechanism to reposition the fusion member to the desired location. Oneof ordinary skill will realize that the delivery mechanism and/orretention mechanism of some embodiments can be used for delivery of anytype of interbody fusion members between two vertebral bodies (e.g.,even those that do not utilize anchoring members).

As mentioned above, the anchoring members (e.g., large gauge needles1-10 mm in outer diameter) are pushed through the channels of thedelivery mechanism and the fusion member and into the marrow space ofthe vertebral bodies, in order to affix the fusion member to thevertebral bodies. Moreover, in some embodiments, polymethyl methacrylate(PMMA) or other bone cement or hardening polymer material, is injectedthrough the anchoring members and into the vertebral bodies. In themarrow space of the vertebral bodies, this injected material forms acloud around the tip of the anchoring member and hardens after aduration of time. Once this injected material hardens, it furthersolidifies the attachment of the fusion member to the vertebral bodies.To facilitate such injections, the anchoring members have hollowchannels and perforated tips in some embodiments.

In some embodiments, the anchoring members are part of an anchoringmechanism that also includes driving members that advance the anchoringmembers through the fusion member channels into vertebral bodies. Someembodiments of the invention provide a coupling mechanism that coupleseach anchoring member to a corresponding driving member. In someembodiments, each driving member includes (1) a shaft that advances theanchoring member fully into the fusion member or withdraws the anchoringmember from the fusion member and (2) a central lumen that provides aconduit for delivering polymers to the anchoring member.

The central lumen in the driving member aligns with the hollow channel(i.e., lumen) in its corresponding anchoring member once the anchoringmember is in its desired position inside a vertebral body. Accordingly,once the driving members push the anchoring members into the vertebralbodies, hardening material (e.g., PMMA, bone cement, or other hardeningpolymer) may be injected through the central lumen of the driving andanchoring members. The polymer flows from the central lumen of thedriving member, through the central lumen of the anchoring member, andinto the marrow space of the vertebral bodies. This material passesthrough the perforations (i.e., openings) of the anchoring member intothe marrow space of the vertebral body, contiguous with or adjacent tothe anchoring member tip that is inside the marrow space. The polymerclouds in some embodiments form a spherical or ellipsoidal “cloud” ofPMMA contiguous with the anchoring member tip. Once the polymer cloudhardens, the surface contours of the anchoring member serve to anchorthis member to the vertebral body and prevent it from being withdrawnfrom the trabecular bone, and thereby enhances the structural integrityof the inserted fusion device yielding solid mechanical fusion.

To enhance the structural integrity of the coupling between the fusiondevice and the vertebral bodies, some embodiments define various surfacecontours along the anchoring member's tip. Examples of such contoursinclude angled teeth and backfacing ridges. These contours (e.g., angledteeth and backfacing ridge) allow the anchoring member to pass throughthe fusion member's channel and into the bone (i.e., into the adjacentvertebral body). In some embodiments, hardening material might not beinjected through the anchoring members. Instead, the insertion of theanchoring members and particular variations for the anchoring tipcontours prevent the anchoring members from being easily withdrawn fromthe bone.

In some embodiments, the anchoring member and driving member coupledtogether form a unified needle. In such an embodiment, the anchoringmember is the embedded portion that is embedded in the vertebral bodieswhile the driving member is the retractable portion that is removed oncethe fusion member has been affixed to the vertebral bodies between whichit is placed.

Once the anchoring members are in place, and the polymers have beeninjected into the marrow space of the vertebral bodies, the drivingmembers and delivery mechanism may be removed, as mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth in the appendedclaims. However, for purpose of explanation, several embodiments of theinvention are set forth in the following figures.

FIG. 1A provides a front perspective of the intervertebral apparatus.

FIGS. 1B and 1C provide different perspectives of an exploded view ofthe intervertebral apparatus.

FIGS. 2-3 illustrate the intervertebral apparatus in relation to twovertebral bodies between which the fusion member is placed.

FIG. 4 illustrates one perspective of the fusion member which includeschannels through which anchoring mechanisms can be inserted andadvanced.

FIGS. 5A-5B provide an illustration of the fusion member and retentiongrooves without the retention rods of the delivery mechanism.

FIG. 6 shows a perspective view of the delivery mechanism coupled withthe fusion member.

FIG. 7A illustrates the delivery housing from the perspective of theoperator.

FIGS. 7B-7C illustrate the delivery housing with two retention rods inthe delivery housing channels from the perspective of the operator andfrom the perspective opposite of the operator.

FIGS. 8-9 provide different perspectives of the retention rod of thedelivery mechanism.

FIGS. 10A-10C (1) illustrate an example of the process of controllablydetaching the delivery mechanism from the fusion member and (2) providea detailed view of one of the retention rods.

FIG. 11 illustrates a detailed view of the retention rod teeth coupledwith the retention groove.

FIG. 12 illustrates a cross-section of the retention rod coupled withthe retention groove.

FIG. 13 shows alternative embodiments of retention teeth of theretention rods.

FIG. 14 shows two anchoring mechanisms in their initial configurationinside the channels of the delivery housing and fusion member.

FIG. 15 shows two anchoring mechanisms in their final configurationafter the anchoring members have been advanced into the vertebralbodies.

FIG. 16 illustrates a perspective view of two anchoring members insidethe fusion member channels.

FIG. 17 depicts two anchoring members that have almost been fullyadvanced through the fusion member channels.

FIG. 18 depicts the flexibility of the anchoring member.

FIGS. 19-21 illustrate different views of the driving members and theanchoring members coupled and decoupled with the intervening members.

FIGS. 22A-22B illustrate exploded views of the pivoting mechanism fromdifferent perspectives.

FIGS. 23A-23B shows the driving members connecting directly with theanchoring members (i.e., no intervening member).

FIGS. 24A-24B shows different views and configurations of couplingmechanisms connected directly with the anchoring members and the drivingmembers.

FIGS. 25A-25D provide detailed illustrations of the coupling mechanism.

FIGS. 26A-C show two anchoring members that have been inserted throughthe fusion member and into the vertebral bodies.

FIGS. 27A-27B depict the placement of one fusion member between adjacentvertebral bodies, a set of two anchoring members that have affixed thefusion member to the vertebral bodies, and the coalescence of thepolymer collections that resulted following injections of the polymersvia anchoring members.

FIGS. 28A-28B depict placement of two fusion members within the rightand left paramedian disc space of adjacent vertebral bodies, multiplesets of anchoring members that have affixed the two fusion members tothe vertebral bodies, and the coalescence of polymer clouds followingthe polymer injections.

FIG. 29 depicts a medical procedure that involves the insertion of theapparatus of some embodiments.

FIGS. 30-33 illustrate different views of an interbody fusion membercomprising curved tubular channels with distal openings on the superiorblock face and inferior block face.

FIG. 34 illustrates a detailed view of the anchoring member tips of oneembodiment.

FIGS. 35-36 illustrate different views of anchoring members that havebeen advanced through the semicircular tubular channels of the fusionmember into the marrow space of the vertebral bodies.

FIG. 37 illustrates PMMA injections through the anchoring members aboveand below the fusion member.

FIGS. 38-40 illustrate different views of an alternative fusion memberembodiment with nonparallel angled curved channels extending to theinferior and superior block faces.

FIGS. 41-42 illustrate different views of an alternative fusion memberembodiment comprising oblique linear channels that are traversed bystraight anchoring members which are rectangular in cross-sectionalprofile.

FIG. 43 illustrates the tip of the straight anchoring members which arerectangular in cross-sectional profile.

FIGS. 44-45 illustrate different views of PMMA that has been injectedand forms collections contiguous with the perforated, contoured tips ofanchoring members within the marrow spaces of adjacent vertebral bodies.

FIGS. 46A, 46B, and 47 illustrate different views of an alternativefusion member embodiment comprising curved tubular channels that run inparallel planes with respect to each other but are nonparallel to theadjacent faces of the fusion block member.

FIGS. 48A-48D illustrate alternative anchoring member tips.

FIG. 49 illustrates various surface contours of the fusion member.

FIG. 50 illustrates an alternative retention rod with retention teeth ofvariable dimensions.

FIG. 51 illustrates an alternative retention rod with retention teeth ofvariable dimensions engaging retention grooves of matching profile in afusion member.

FIG. 52 shows a fusion member with four channels and four anchoringmembers that are advanced into these fusion member channels.

FIG. 53 shows four anchoring members that have been inserted through thefusion member and into the vertebral bodies.

FIG. 54 depicts the placement of one fusion member between adjacentvertebral bodies, a set of four anchoring members that have affixed thefusion member to the vertebral bodies, and the coalescence of thepolymer collections that resulted following injections of the polymersvia anchoring members.

FIG. 55 depicts placement of two fusion members within the right andleft paramedian disc space of adjacent vertebral bodies, multiple setsof anchoring members that have affixed the two fusion members to thevertebral bodies, and the coalescence of polymer clouds following thepolymer injections.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous details are set forth to providea better understanding of the various embodiments of the invention.However, one of reasonable skill in the art will realize that theinvention may be practiced without the use of the specific detailspresented herein. In some instances of describing the invention,well-known structures may be omitted or shown in block diagram form toavoid obscuring the description of the invention with unnecessarydetail. Therefore, the examples provided herein for description andclarification should not be interpreted as in anyway limiting thelanguage of the claims.

I. Overview

Some embodiments of the invention provide an apparatus that (1) deliversa fusion member between two vertebral bodies after at least a portion ofthe fibrocartilaginous disc between the vertebral bodies has beenremoved, and (2) affixes the fusion member to the vertebral bodies. Insome embodiments, the apparatus includes (1) a fusion member that isdelivered and positioned between the vertebral bodies, (2) a deliverymechanism that delivers and positions the fusion member between thevertebral bodies, and (3) an anchoring member that affixes the fusionmember to vertebral bodies.

In some embodiments, the interbody fusion member is a shaped block(e.g., a rectangular or oblong block) with one or more channels (e.g.,tubular channels). As mentioned above, this member is placed betweenendplates of adjacent vertebrae following a partial or completediscectomy. In this position, two or more sides of the fusion member arein contact with the opposed endplates. These contacting sides may beparallel to each other, or nonparallel such that the fusion memberpresents a tapered profile when viewed laterally so as to restore bothdisc height and physiologic lordosis. In this position, one or moreanchoring members (e.g., one or more open-tipped or close-tippedneedles) can be pushed through the one or more channels of the fusionmember and into the marrow space of one or more of the vertebral bodies,in order to affix the fusion member to the vertebral bodies. This isfurther described below.

In some embodiments, the delivery mechanism that delivers the fusionmember between vertebral bodies includes (1) a delivery housing thathouses the anchoring mechanism and (2) a retention mechanism thatcouples the delivery housing to the fusion member. In some embodiments,the delivery housing also includes channels that guide retention rods ofthe retention mechanism of some embodiments.

In some embodiments, the retention rods have retention teeth that matewith retention grooves on the fusion member. The retention rods,grooves, and teeth form the retention mechanism of some embodiments.Other embodiments might have different retention mechanisms. Forinstance, in some embodiments, the retention teeth are on the fusionmember while the retention grooves are on the retention rod. Moreover,instead of, or in conjunction with, this tooth and groove approach, oneof ordinary skill will realize that other embodiments use otherretention structures (e.g., other male/female structures, otherstructures such as expandable clasps that encapsulate the lateral edgesof the fusion member, other structures such as a clamp, etc.) to affixthe delivery mechanism to the fusion member.

The retention mechanism is used in some embodiments as a way ofcontrollably detaching the delivery mechanism from the fusion memberafter the medical practitioner (1) determines that the fusion member isplaced at the desired position between two vertebral bodies, and (2)inserts the anchoring members into the vertebral bodies in order toaffix the fusion member to the vertebral bodies. When the medicalpractitioner determines (e.g., by viewing x-ray images of the patient)that the fusion member is not placed at an appropriate position betweentwo vertebral bodies, he can use the delivery mechanism to repositionthe fusion member to the desired location. One of ordinary skill willrealize that the delivery mechanism and/or retention mechanism of someembodiments can be used for delivery of any type of interbody fusionmembers between two vertebral bodies (e.g., even those that do notutilize anchoring members and/or PMMA or bone cement).

As mentioned above, the anchoring members (e.g., large gauge needles1-10 mm in outer diameter) are pushed through the channels of thedelivery mechanism and the fusion member and into the marrow space ofthe vertebral bodies, in order to affix the fusion member to thevertebral bodies. Moreover, in some embodiments, polymethyl methacrylate(PMMA) or other bone cement or hardening polymer material, is injectedthrough the anchoring members and into the vertebral bodies. In themarrow space of the vertebral bodies, this injected material forms acloud around the tip of the anchoring member and hardens after aduration of time. Once this injected material hardens, it furthersolidifies the attachment of the fusion member to the vertebral bodies.To facilitate such injections, the anchoring members have hollowchannels and perforated tips in some embodiments.

In some embodiments, the anchoring members are part of an anchoringmechanism that also includes driving members that advance the anchoringmembers through the fusion member channels into vertebral bodies. Someembodiments of the invention provide a coupling mechanism that coupleseach anchoring member to a corresponding driving member. In someembodiments, each driving member includes (1) a shaft that advances theanchoring member fully into the fusion member or withdraws the anchoringmember from the fusion member and (2) a central lumen that provides aconduit for delivering polymers to the anchoring member.

The central lumen in the driving member aligns with the hollow channel(i.e., lumen) in its corresponding anchoring member once the anchoringmember is in its desired position inside a vertebral body. Accordingly,once the driving members push the anchoring members into the vertebralbodies, hardening material (e.g., PMMA, bone cement, or other hardeningpolymer) may be injected through the central lumen of the driving andanchoring members. The polymer flows from the central lumen of thedriving member, through the central lumen of the anchoring member, andinto the marrow space of the vertebral bodies. This material passesthrough the perforations (i.e., openings) of the anchoring member intothe marrow space of the vertebral body, contiguous with or adjacent tothe anchoring member tip that is inside the marrow space. The polymerclouds in some embodiments form a spherical or ellipsoidal “cloud” ofPMMA contiguous with the anchoring member tip. Once the polymer cloudhardens, the surface contours of the anchoring member serve to anchorthis member to the vertebral body and prevent it from being withdrawnfrom the trabecular bone, and thereby enhances the structural integrityof the inserted fusion device yielding solid mechanical fusion.

To enhance the structural integrity of the coupling between the fusiondevice and the vertebral bodies, some embodiments define various surfacecontours along the anchoring member's shaft. Examples of such contoursinclude angled teeth and backfacing ridges. These contours (e.g., angledteeth and backfacing ridge) allow the anchoring member to pass throughthe fusion member's channel and into the bone (i.e., into the adjacentvertebral body). In some embodiments, hardening material might not beinjected through the anchoring members. Instead, the insertion of theanchoring members and particular variations for the anchoring tipcontours prevent the anchoring members from being easily withdrawn fromthe bone.

In some embodiments, the anchoring member and driving member coupledtogether form a unified entity, the anchoring member. In such anembodiment, the anchoring member is the embedded portion that isembedded in the vertebral bodies while the driving member is theretractable portion that is removed once the fusion member has beenaffixed to the vertebral bodies between which it is placed.

Once the anchoring members are in place, and the polymers have beeninjected into the marrow space of the vertebral bodies, the drivingmembers and delivery mechanism may be removed, as mentioned above.

One of ordinary skill will realize that although several embodimentshave been described above, other embodiments might be implemented oroperated differently. For instance, before advancing the anchoringmembers into the vertebral bodies as described above, some embodimentsfirst advance a smaller gauge anchoring member into the marrow space ofthe adjacent vertebral body before placement of the larger gaugeanchoring member. This creates a guide to help ensure that the largergauge anchoring member will be advanced into the proper position withinthe trabecular bone of the vertebral body.

To better understand these embodiments, it is helpful to understandrelevant terminology and describe examples of the invention in use.Therefore, the following sections present relevant terminology, andprovide an overview of an exemplary fusion procedure of some embodimentsand of a number of more specific design features and variations.

II. Definitions and Terminology

The spinal column of humans and other vertebrates comprises vertebralbodies and posterior osseous elements that provide structural supportand also serve to protect the spinal cord and other spinal canalcontents. The vertebral bodies are the cylindrical segmental osseousstructures that form the anterior margin of the spinal canal and areseparated from each other by fibrocartilaginous intervertebral discs. Inthe present discussion, the term “fusion member” refers to a devicepositioned between vertebral bodies. In some embodiments, the fusionmember has one or more channels for the passage of contoured anchoringmembers and/or the retention and positioning of bone graft material orbone graft substitutes between adjacent vertebral bodies.

III. Components of the Fusion Member, Delivery Mechanism, and AnchoringMember(s)

Some embodiments of the invention provide an apparatus that (1) deliversa fusion member between two vertebral bodies after at least a portion ofthe fibrocartilaginous disc between the vertebral bodies has beenremoved, and (2) affixes the fusion member to the vertebral bodies.

FIGS. 1-3 illustrate an example of one such apparatus according to someembodiments. FIG. 1A provides a front view of the apparatus 110. FIGS.1B and 1C provide different perspectives of an exploded view of theapparatus 110. FIG. 2 provides a side view of the apparatus 110 inrelation to two vertebral bodies 210-220 between which a fusion member120 is placed. FIG. 3 provides a rear view of the apparatus 110 inrelation to the two vertebral bodies 210-220 between which the fusionmember 120 is placed.

As shown in these figures, the apparatus 110 includes (1) a fusionmember 120 that is delivered and positioned between the vertebral bodies210-220, (2) a delivery mechanism 130 that delivers and positions thefusion member 120 between the vertebral bodies 210-220, and (3)anchoring mechanisms 140 that affix the fusion member 120 to thevertebral bodies 210-220. Each of these components will be described infurther detail below.

A. Fusion Member

As mentioned above, the apparatus 110 includes a fusion member 120 thatis delivered and positioned between the vertebral bodies 210-220. Thefusion member 120 includes (1) two channels 170 through which twoanchoring mechanisms can be advanced, and (2) retention grooves 150 of aretention mechanism for attaching the fusion member to the deliverymechanism.

FIG. 4 illustrates a perspective view of the fusion member 120 of someembodiments of the invention. In this and some of the subsequentfigures, fusion members are shown transparently to facilitate anappreciation of the spatial relationships between multiple channels andtheir openings upon multiple faces of the fusion member.

As shown in FIG. 4, the fusion member 120 includes channels 410 and 440through which anchoring mechanisms can be inserted and advanced. Channel410 has a distal opening 420 on the superior face 430 of the fusionmember 120. Channel 440 has a distal opening 450 on the inferior face460 of the fusion member 120. Channel 410 has a proximal opening 470 onthe proximal face 490 of the fusion member 120. Channel 440 also has aproximal opening 480 on the proximal face 490 of the fusion member 120.Some embodiments of the fusion member provide a recess of increaseddiameter (e.g., flange cavity, anchoring member cavity, etc.) on thechannel opening on the proximal face of the fusion member (one suchexample will be described below by referring to the anchoring membercavity 1685-1690 of FIG. 16 and the anchoring member cavity 1720 of FIG.17).

As shown in the example illustrated in FIG. 4, the cross-sectionalplanes of the fusion member channels 410 and 440 are parallel to eachother, but are not parallel to the right and left face of the fusionmember 120. This allows the distal opening 420 of channel 410 to belocated on the center of the superior 430 face of the fusion member, andthe distal opening 450 of channel 440 to be located on the center of theinferior 460 face of the fusion member even though their proximalopening 470 and 480 start on the same proximal face 490. Even though thefusion member channels shown in these figures are curved and tubular,one of ordinary skill in the art will know that the channels may beother shapes or configurations in other embodiments as later describedin Section V.

FIG. 5A provides an illustration of the fusion member 120 and two setsof retention grooves 150 located on the left side of the fusion member120 without the retention rods of the delivery mechanism. The two setsof retention grooves on the right side of the fusion member are notshown in this figure. FIG. 5B provides a front perspective of the fusionmember 120 with the two sets of retention grooves 150 located on theleft side of the fusion member 120 and two sets of retention grooves 150located on the right side of the fusion member 120. The two sets ofretention grooves couple with the retention rods of the deliverymechanism. Both the delivery mechanism and the retention rods will bedescribed in further detail below.

As shown in FIGS. 5A-5B, each set of retention grooves 150 includes twosubsets of grooves (i.e., indentations, cavities, etc.) that differ indiameter, a first set of grooves 520 having a smaller diameter than asecond set of grooves 510. These figures show the first subset ofgrooves 520 with six indentations that are smaller in diameter than thesecond subset of grooves 510 with five indentations that are larger indiameter. The first subset of grooves 520 couples with the shaft of aretention rod while the second subset of grooves 510 couples with theteeth of the retention rod as further described below. In someembodiments, the retention grooves of the fusion member couple withretention rods of the delivery mechanism to form a retention mechanism.The retention teeth of the rods are the male coupling members of theretention mechanism while the retention grooves of the fusion membersare the female coupling members of this mechanism.

In the example illustrated in FIGS. 5A-5B, two subsets of retentiongrooves 150 are located on the left side of the fusion member and twosubsets of retention grooves are located on the right side of the fusionmember. However, one of ordinary skill in the art will realize that theretention mechanism and retention grooves can be in another location onthe fusion member, such as in the interior of the fusion member, and canvary in shape, size, and number. Also, other embodiments might havedifferent retention mechanisms. For instance, in some embodiments, theretention teeth are on the fusion member while the retention grooves areon the retention rod. Moreover, instead of, or in conjunction with, thistooth and groove approach, one of ordinary skill will realize that otherembodiments use other retention structures (e.g., other male/femalestructures, other structures such as expandable clasps that encapsulatethe lateral edges of the fusion member, other structures such as aclamp, etc.) to affix the delivery mechanism to the fusion member.

Also, in the example illustrated in FIG. 5B, the cross-sectional view ofthe two channels 530 that go through the fusion member 120 are parallelto the right and left side of the fusion member 120. This is a differentchannel implementation than the channels 410 and 440 of the exampleillustrated in FIG. 4. As mentioned above, the cross-section planes ofthose two channels 410 and 440 are not parallel to the right and leftsides of the fusion member, even though they are parallel to each other.

In some embodiments, the fusion member can be composed of any number ofmaterials, such as metals (e.g., stainless steel, titanium, or nitinol),various polymers (e.g., PMMA or polyetheretherketone), carbon fiber,etc. The fusion member can also be partially or be completely made ofbioabsorbable or biodegradable materials, so that it can be partially orbe completely absorbed. In some embodiments, the fusion member's facesthat are in contact with the vertebral endplates may have surfacecontours such as ridges to enhance stability. The fusion member can alsoinclude additional channels or cavities to be packed with bone graftmaterial or bone graft substitutes to enhance progressive solid bonyfusion. Bone graft material and bone graft substitutes can also bepacked into the intervertebral space surrounding and between the fusionmembers to enhance progressive solid bony fusion. The fusion member canalso be coated with or partially be composed of human bone morphogeneticprotein or other bone growth inducing substances.

Typically, the fusion member is inserted between adjacent vertebralbodies after at least some of the fibrocartilaginous disc between theadjacent vertebral bodies is removed during a partial or completediscectomy. Once the fusion member is delivered to the proper locationbetween adjacent vertebral bodies, two or more sides of the fusionmember may be in contact with the opposed endplates of the adjacentvertebral bodies. These contacting sides in some embodiments restoreboth disc height and physiologic lordosis. In some embodiments, thesesides are parallel to each other, whereas in other embodiments, thesesides are nonparallel such that the fusion member presents a taperedprofile when viewed laterally. The delivery mechanism that inserts thefusion member between the vertebral bodies will be described below.

B. Delivery Mechanism

As mentioned above, the delivery mechanism delivers the fusion memberbetween adjacent vertebral bodies. FIG. 6 shows a perspective view ofthe delivery mechanism 130 coupled with the fusion member 120. Thedelivery mechanism includes (1) a delivery housing 610 that houses theanchoring mechanism and retention rods 160, and (2) four retention rods160 that couple the delivery housing 610 with the fusion member 120.From this perspective, only three of the four retention rods can beseen.

FIG. 7A illustrates the delivery housing 610 from the perspective of theoperator during an operation (i.e., the backside of the deliverymechanism during an operation). FIGS. 7B and 7C illustrate the deliveryhousing with two retention rods 160 in channels 710 from the perspectiveof the operator and from the perspective opposite of the operator duringan operation (i.e., from the front side of the delivery mechanism duringan operation).

As shown in FIGS. 7A and 7B, the delivery housing 610 includes circularchannels 710 and 720 that run the entire length of the delivery housing610, from the distal end of the delivery housing to the proximal end ofthe delivery housing. In some embodiment, these channels have the samediameter throughout the entire length of the channel. The two channels720 house and guide the anchoring mechanism (not pictured) to the properchannel opening of the fusion member, whereas the four channels 710house and retain the retention rods. One of ordinary skill in the artwill realize that any number of channels that house the retention rodsand the anchoring mechanism can be used. The delivery housing channelscan be of various shapes and sizes to accommodate the various shapes andsizes of the anchoring mechanism and retention rods. The anchoringmechanism will be described in further detail in Section C.

As mentioned above, the retention mechanism attaches the deliveryhousing to the fusion member. In some embodiments, the retentionmechanism is used as a way of controllably detaching the deliverymechanism from the fusion member after the medical practitionerdetermines that the fusion member is placed at the desired positionbetween two vertebral bodies.

The retention mechanism that is illustrated in FIGS. 6-7 includes (1)retention rods 160 of the delivery mechanism 130, and (2) sets ofretention grooves 150 of the fusion member 120, which couple withretention rods 160 of the delivery mechanism 130. As shown in FIGS. 8-9each retention rod in some embodiments includes (1) a shaft 810 with adistal end that couples with the subset of smaller retention grooves520, (2) retention teeth 815 on the distal end of the shaft 810 thatcouple with the subset of larger retention grooves 510, and (3) a handle820 on the proximal end of the shaft that rotates the retention rod.

FIGS. 10A-10C step through an example of the process of controllablydetaching the delivery mechanism 130 from the fusion member 120 once thedelivery mechanism is no longer needed. FIG. 10A shows the initialconfiguration of two retention rods 160 of the delivery mechanism 130fully coupled with two sets of retention grooves of the fusion member120. In this figure, the retention rod 160 is fully coupled withretention grooves of the fusion member 120. In this configuration, thedelivery rod 160 and delivery housing (e.g., the delivery mechanism 130)is tightly coupled with the fusion member 120. This configuration allowsthe fusion member 120 to be delivered between adjacent vertebral bodies.After the fusion member 120 has been delivered, a medical practitionerdetermines (e.g., by viewing x-ray images of the patient) whether thefusion member is in the correct position. If a determination is madethat fusion member is not in the correct position between two vertebralbodies, the delivery mechanism can be used to reposition the fusionmember to the desired location. When the medical practitioner determinesthat the fusion member is placed at the desired position between twovertebral bodies, and anchoring members have affixed the fusion memberto the vertebral bodies, the retention mechanism can be used tocontrollably detach the delivery mechanism 130 from the fusion member120. The controllable detachment of the delivery mechanism from thefusion member is initiated by the uncoupling of each retention rod fromeach set of retention grooves.

FIG. 10B shows a single retention rod 160 partially uncoupled from theretention grooves of the fusion member. In this configuration, theretention rod 160 is rotated 180 degrees so that the retention teeth 910are disengaged from the subset of larger retention grooves 510. Thisconfiguration allows the retention rod 160 to be withdrawn from theretention grooves of the fusion member.

FIG. 10C shows the distal end of the shaft of the retention rod 160after the shaft has been pulled away from the fusion member so that itis barely in contact with the subset of smaller retention grooves 520(i.e., it has been removed from all but the last smaller retentiongroove). Once the shaft of the retention rod has been withdrawn from theretention grooves and from the fusion member, the process can berepeated to uncouple the remaining retention rods from the fusionmember. When all of the retention rods have been uncoupled from thefusion member, the delivery mechanism can be detached from the fusionmember and removed from the patient.

FIGS. 11-12 illustrate another example of the retention grove and teethstructures of some embodiments. In this example, the retention teeth1115 encompass less than 180 degrees of the retention rod shaft. Thisfacilitates clearance between the retention teeth 1115 and thelarger-diameter retention grooves 1110 when uncoupling the retentionteeth 1115 from these grooves 1110 and when withdrawing the retentionrod 160 away from the fusion member and out of the smaller-diameterretention grooves 1120. This example also shows the flared shape of thesubset of larger retention grooves 1110. The flared shape of theretention grooves 1110 match the flared shape of the retention teeth1115 in order to secure the retention teeth 1115 to the retentiongrooves 1110.

FIG. 12 illustrates a cross-section of the retention teeth 1115 fullycoupled with the larger-diameter retention grooves 1110 to show theflared shape of the retention teeth. The width of the retention teethincreases as the distance increases from its base 1210 (i.e., where theretention teeth 1115 attach to the retention rod 160). The tip 1220 ofeach retention tooth has the largest width while the base 1210 of eachretention tooth has the smallest width. This flared shape prevents anymovement of the retention rod along the plane of the x, y, or z axis(i.e., prevents any horizontal or vertical movement, including theoutward lateral movement of the retention rod from the fusion member)when the teeth of the retention rod are fully coupled with thelarger-diameter retention grooves.

One of ordinary skill in the art will realize that even more alternativestructures can be used for the retention groove and teeth structuresthan those illustrated in FIGS. 8-12. For instance, FIG. 13 illustratesa number of other teeth structures that are used in some embodiments.

Moreover, one of ordinary skill in the art will also realize thatdifferent configurations and different numbers of retention teeth can beutilized to affix the delivery mechanism to the fusion member. In someembodiments, the retention teeth may be on the fusion member and theretention groove may be on the retention rod. Instead of, or inconjunction with, this tooth and groove approach, other embodiments ofthe invention can use other structures (e.g., other male/femalestructures, other structures such as expandable clasps that encapsulatethe lateral edges of the fusion member, other structures such as aclamp, etc.) to affix the delivery mechanism to the fusion member.

As mentioned above, the delivery housing channels house and guide theanchoring mechanism to the proper location in the fusion member.Different embodiments have different housing channels for guiding theanchoring mechanism to the proper location in the fusion member. In someembodiments, a circular channel with a constant diameter throughout itsentire length can guide the anchoring mechanism as shown in FIGS. 7A-7C.Other embodiments have channels of different shapes and sizes. One suchalternative embodiment is a square or rectangular channel withincreasing and decreasing diameter towards the distal end of thedelivery housing as will be described in the next section in referenceto FIG. 14.

C. Anchoring Mechanism

Different embodiments of the invention use different anchoringmechanisms. Some embodiments use an anchoring mechanism formed by threepieces—an anchoring/embedded member, an intervening member, and adriving/retractable member. In some embodiments, the anchoring/embeddedmember, intervening member, and the driving/retractable member couplewith each other to form a unified needle.

Other embodiments use an anchoring mechanism formed by two pieces—ananchoring/embedded member and a driving/retractable member. In someembodiments, the anchoring/embedded member and the driving/retractablemember couple with each other to form a unified needle. The differentembodiments of the anchoring mechanism will now be described in detailbelow.

1. Pivoting Anchoring Mechanism with Intervening Member

As mentioned above, some embodiments use an anchoring mechanism formedby three pieces—an anchoring/embedded member, an intervening member, anda driving/retractable member. FIG. 14 shows one such embodiment of theanchoring mechanism. In this figure, two anchoring mechanisms are intheir initial configuration inside the channels 1465 and 1475 of thedelivery housing 610 and the fusion member 120. The anchoring mechanismsinclude (1) anchoring members 1410-1420 that affix the fusion member 120to adjacent vertebral bodies, (2) intervening members 1470 and 1480, and(3) driving members 1430-1440 that advance the anchoring members1410-1420 through the fusion member channels into the vertebral bodies.The driving members 1430-1440 include (1) shafts that advance theanchoring members 1410-1420 fully into the fusion member 120 or withdrawthe anchoring members 1410-1420 from the fusion member 120 and (2)central lumens that provide a conduit for delivering polymers to theanchoring members 1410-1420. The intervening members 1470 and 1480 havecentral lumens (e.g., channels) as well. The central lumen in thedriving members 1430-1440 and intervening members 1470 and 1480 alignwith the hollow channels (i.e., lumen) of their corresponding anchoringmembers 1410-1420 once the anchoring members 1410-1420 are advanced totheir desired position inside the vertebral bodies.

Two delivery housing channels are shown in this figure. The firstchannel is shown with an opening 1465 on the proximal end of thedelivery housing. The second channel is shown with the opening 1475 alsoon the proximal end of the delivery housing. Moreover, in FIG. 14, bothchannels are shown as transparent so that the second driving andanchoring members can be seen. However, these channels are similar tothe channels 720 in FIGS. 7A-7C, except for their shape, which isfurther described below.

In some embodiments, the anchoring members are initially configured tobe inserted in the entirety of the fusion member channels or in part ofit, during the manufacturing of the fusion member delivery apparatusthat contains these anchoring members. In other embodiments, they areinitially configured to be fully contained in the housing of thedelivery mechanism before they are inserted into the fusion member ontheir way for inserting into the vertebral bodies during an operation.

FIG. 15 shows the anchoring mechanisms in a configuration after theanchoring members 1410-1420 have been advanced into the vertebral bodies(which are not shown in this figure). When the anchoring mechanisms arefully advanced, the tips of the anchoring members 1410-1420 extend outof the fusion member channels and beyond the boundaries of the fusionmember 120 into the marrow space of adjacent vertebral bodies. In thisconfiguration; the anchoring members 1410-1420, the driving members1430-1440, and intervening members 1470 and 1480 as well as theircentral lumens are aligned. This alignment provides an unobstructedpathway for the polymer to flow from the driving members 1430-1440through the intervening members 1470 and 1480 and into the anchoringmembers 1410-1420.

FIGS. 14 and 15 also show an alternative embodiment of the deliveryhousing channels as mentioned above. As shown in these figures, thedelivery housing channels 1465 and 1475 has two sections 1510 and 1520.A first section 1510 of the delivery housing channel has a diameter thatincreases towards the distal end of the delivery housing 610 (i.e., hasincreasing cross sections along the anchoring mechanism's path of themovement). In this section, the top side and bottom side of the deliveryhousing channel taper away from each other (i.e., the top side inclinesaway from the proximal opening while the bottom side declines away fromthe proximal opening). The increasing diameter provides sufficient spaceto allow the anchoring members 1410 and 1420 and the intervening members1470 and 1480 to be at an angle with the driving members 1430 and 1440as shown in its initial configuration. In addition, the increaseddiameter provides sufficient space to allow the anchoring members 1410and 1420 and the intervening members 1470 and 1480 to pivot with thedriving members 1430 and 1440.

A second section 1520 of the delivery housing channel has a diameterthat decreases towards the distal end of the delivery housing 610 (i.e.,has decreasing cross sections along the anchoring mechanism's path ofmovement). In this section, the top side and bottom side of the deliveryhousing channel taper toward each other (i.e., the top side declinestowards the distal opening while the bottom side inclines towards thedistal opening). The tapered (i.e. angled) top and bottom sides of thissection (1) allow the anchoring member to pivot at an angle with thedriving member and (2) guide the driving member towards the distalopening of the delivery housing channel. In some embodiments, eachchannel's longitudinal cross-section (i.e., cross-section that runs thelength of the delivery housing) is in the shape of two trapezoids wherethe bases of the trapezoids are facing each other.

The transition of the anchoring mechanism from its initial configurationto its final configuration involves the tapered sides of the deliveryhousing channel's second section. As mentioned above, the tapered topand bottom sides of the second section allow the anchoring member topivot with the driving member. While the anchoring mechanism is in itsinitial configuration illustrated in FIG. 14, force can be applied tothe driving member in a first direction illustrated in FIG. 14 toadvance the driving member towards the distal end of the deliveryhousing channel. When the driving member is advanced to the taperedsides of the delivery housing channel's second section, the taperedsides cause the anchoring member to pivot at an angle with the drivingmember. As the driving member is further advanced in this firstdirection, the distal end of the driving member travels down the taperedside toward the distal opening of the delivery housing. Since theanchoring member is at an angle with the driving member, the anchoringmember is advanced in a second curvilinear direction that is at an anglewith the first direction. The anchoring member is advanced through thecurved fusion member channel and into the vertebral body. As the fusionmember channel is curved, the path that the anchoring member travels isalso curved. In other words, the anchoring member traverses in a seconddirection that is curved throughout its advancement through the fusionmember channel. Accordingly, from the initial configuration of theanchoring mechanism to its final configuration, the tip of the anchoringmember travels in a semi-circular path of movement.

Once the driving members 1430-1440 push the anchoring members 1410-1420into the vertebral bodies, hardening material (e.g., PMMA, bone cement,or other hardening polymer) may be injected through the central lumen ofthe driving members, through the central lumen of the anchoring members,and into the marrow space of the vertebral bodies.

FIG. 16 illustrates a perspective view of the anchoring members1410-1420. As shown in this figure, the anchoring members 1410-1420 have(1) several (e.g., three) distal perforations 1605-1630, (2) centrallumens 1635-1640, (3) flanged bases 1645-1650, and (4) female couplingcomponents 1655-1660 that couple with male coupling components ofintervening or driving members, as further described below.

The distal perforations 1605-1630 of the anchoring members 1410-1420communicate directly with the central lumens 1635-1640 of the anchoringmember. These lumens 1635-1640 extend from the distal perforations1605-1630 to the flanged bases 1645-1650 and their proximal openings1665-1670. Polymer material can be injected through the central lumen ofthe driving and intervening members, into the openings 1665-1670 of theanchoring members 1410-1420, through the central lumens 1635-1640 of theanchoring members 1410-1420, and out of the perforations 1605-1630 to bedelivered to the marrow space of vertebral bodies.

As shown in FIG. 16, the anchoring members 1410-1420 in some embodimentshave surface contours 1675-1680 along their distal segment. In someembodiments, these surface contours may be angled teeth, back-facingretention ridges, or other surface contours. These surface contoursassist in the retention of the anchoring members 1410-1420 within thevertebral bodies after injection and hardening of PMMA thereby furthersolidifying the anchoring of the fusion member 120 between the vertebralbodies.

As shown in FIG. 16, flanges 1645-1650 at the base of the anchoringmembers 1410-1420 fit into recesses (i.e., flange cavity, anchoringmember cavity, etc.) 1685-1690 of the fusion member channels locking theanchoring members 1410-1420 to the fusion member 120 once the anchoringmembers are fully advanced through the fusion member's channels. FIG. 17illustrates the flange cavities 1720 at the proximal end of each fusionmember channel 1730 that aid in affixing each anchoring member to thefusion member 120 when the anchoring members are fully advanced. In thisfigure, the anchoring members have not been fully advanced through thefusion member's channels to provide a clear illustration of fusionmember's flange cavities 1720 and the flange bases 1710 of the anchoringmembers.

In some embodiments, the flange cavity's shape and the anchoringmember's base shape may slightly differ. This shape difference stillallows the anchoring member to be inserted into fusion member channel,but provides friction between the flange base of the anchoring memberand the flange cavity of the fusion member channel, when the anchoringmember has been fully advanced, to lock the anchoring member to thefusion member. In some embodiments, the flange cavity may have at leastone tooth (not pictured) protruding toward the center of the cavityopening that locks the anchoring member to the fusion member when theanchoring member is fully advanced through the fusion member's channels.In addition, this tooth prevents the anchoring member from rotating whenthe driving member is uncoupled from the anchoring member, which will bedescribed detail in FIGS. 24A-24B.

In some embodiments, the anchoring member can be composed of a materialor a combination of materials that provides flexibility as shown in FIG.18. To provide flexibility, the anchoring member can be composed ofmaterials such as nitinol, stainless steel, titanium or other metals,metallic alloys, or high density polymers, carbon fiber, collagen orother biological materials, completely absorbable or partiallyabsorbable material, or of a combination of these materials. In someembodiments, the tip of the anchoring member may be open or closed.

As mentioned above, some embodiments of the invention provide couplingmechanisms that couple the anchoring members directly to theircorresponding driving members 1430-1440. As illustrated in FIG. 14,other embodiments include intervening members 1470-1480 that (1) couplethe driving members 1430-1440 with the anchoring members 1410-1420 and(2) provide pivoting mechanisms 1490-1495 for enabling the anchoringmembers 1410-1420 and the intervening members 1470-1780 to pivot withthe driving members 1430-1440. In some embodiments, the anchoringmembers, driving members, and intervening members all couple together toform a unified needle.

FIGS. 19-21 illustrate the driving members 1900 and the anchoringmembers 1910 coupled with the intervening members 1920. As shown inthese figures, each driving member includes a shaft 2030 that canadvance the anchoring member 1910 fully into the fusion member (notpictured) and can withdraw the anchoring member 1910 partially or fullyfrom the fusion member. Each driving member also includes two pins 2020that mate with two holes in an intervening member 1920 to enable thepivoting of the intervening member 1920 about the driving member 1900.Lastly, each driving member includes a central lumen 2110 (as shown inFIG. 21) that provides a conduit for delivering polymers to theanchoring member 1910. The central lumen extends the entire length ofthe driving member 1900, the intervening member 1920, and the anchoringmember 1910.

FIGS. 20-21 show different views of the distal end of the driving member1900 and the intervening member 1920 in relation to the anchoring member1910. In these figures, the driving member 1900 and intervening member1920 are shown in their coupled and decoupled configurations with theanchoring member 1910. The driving member 1900 and the interveningmember 1920 couple via the coupling mechanism 1450. The couplingmechanism includes a male member 2010 located on the intervening member1920 and a female member 2015 located on the anchoring member 1910. Themale member 2010 includes a protruding stub encompassing the centrallumen 2110 of the intervening member 1920. It also includes an arm 2040and a slot 2060 behind the arm 2040. The female member 2015 includes anindentation that leads to the central lumen 2110 of the anchoring member1910. It also includes an arm 2050 and a slot behind the arm 2070 thatcomplements and rotatably couples with the slot 2060 and the arm 2040 ofthe male member 2010. To separate the coupling mechanism 1450, theintervening member 1920 may be rotated by rotating the driving membershaft 2030 until the interlocking arms 2040-2050 exit the slots2060-2070 in which they were inserted, and the arms 2040 of the malemember 2010 and arms 2050 of the female member 2015 clear each other, asfurther described below by reference to FIGS. 24A-24B.

The intervening member 1920 also includes two holes that mate with thetwo pins of the driving member. As mentioned above, the mating allowsthe intervening member 1920 to pivot with the driving member 1900 andadditionally couples the driving member 1900 with the intervening member1920. FIGS. 22A-22B illustrate exploded views of the pivoting mechanismfrom different perspectives. As shown in these figures, the pivotingmechanism comprises protruding pegs (i.e., pins) 2210 on the distal endof the driving member shaft, and holes 2220 for engaging the pegs 2210.In some embodiments, the protruding pegs 2210, and the holes 2220 areround to allow the intervening member 1920 to pivot around the drivingmember 1900. In some embodiments, the distal end of the driving membershaft is rounded at the tip 2230, and fits into a rounded concaveindentation 2240 of the intervening member 1920. This also facilitatesthe pivoting motion between the intervening member 1920 and the drivingmember 1900. The pivoting movement between the driving member 1900 andthe intervening member 1920 facilitates the advancement of the anchoringmembers 1910 through the channels of the fusion member in a circularmotion.

Once the anchoring member 1910 has been fully advanced through thefusion member channels and into the vertebral bodies, the pivotingmechanism aligns the driving members 1900, intervening members 1920, andthe anchoring members 1910 as illustrated in FIG. 19. This alignmentallows the central lumens 2110 of the driving members 1900, theintervening members 1920, and the anchoring members 1910 to align,providing an unobstructed pathway for the delivery of polymer throughthe driving members 1900, the intervening members 1920, and theanchoring members 1910 into the vertebral bodies.

2. Non-Pivoting Anchoring Mechanism

In some embodiments, the driving members 2320 connect directly to theanchoring members 2310 (i.e., no intervening member) as shown in FIGS.23A-23B. When coupled together, the anchoring member and driving memberform a unified entity, the anchoring needle. In some embodiments, theanchoring member is the embedded portion that is embedded in thevertebral bodies while the driving member is the retractable portionthat is removed once the fusion member has been affixed to the vertebralbodies between which it is placed.

In the embodiment illustrated in FIGS. 23A-23B, the driving member'sdistal end includes the male member 2510 which directly couples with thefemale member 2520 of the anchoring member 2310 (the male member 2510and female member 2520 are shown clearly in FIGS. 25A-25D). The malemember 2510 of the coupling mechanism is directly integrated into thedistal end of the driving member. The female member of the couplingmechanism is directly integrated into the proximal end of the anchoringmember.

In FIGS. 24A-24B, three configurations of the coupling mechanism 1450are shown. These figures illustrate a fully coupled configuration 2450of the anchoring member with the driving member, a partially coupledconfiguration 2460, and a fully decoupled configuration 2470. FIGS.25A-25D provide detailed illustrations of the coupling mechanism.

As shown in FIGS. 24-25, the coupling mechanism 1450 couples theanchoring member with the driving member. A similar coupling mechanism1450 was mentioned above for coupling intervening member 1920 andanchoring member 1910 of FIG. 19. In FIGS. 24-25, the coupling mechanismincludes a male member 2510 and a female member 2520. The male memberincludes a protruding stub encompassing the central lumen of the drivingmember. It also includes an arm 2530 and a slot 2550 behind the arm2530. The female member 2520 includes an indentation that leads to thecentral lumen of the anchoring member. It also includes an arm 2540 anda slot 2560 behind the arm 2540 that complements and rotatably coupleswith the slot 2550 and the arm 2530 of the male member 2510.

As mentioned above, the coupling mechanism is integrated into the distalend of the driving member in some embodiments (e.g. anchoring needle inFIGS. 24A-24B), while other embodiments utilize the intervening memberand integrate the coupling mechanism into the intervening member. Ineither configuration, the anchoring member may detach from the drivingmember or intervening member by separating the coupling mechanism. Toseparate the coupling mechanism, the driving member shaft may be rotateduntil the interlocking arms 2530-2540 exit the slots 2550-2560 in whichthey were inserted, and the arms 2530 of the male member 2510 and arms2540 of the female members 2520 clear each other, as shown in theconfiguration 2460 of FIGS. 24A-24B. Once the interlocking arms areclear of each other, the driving member and the intervening member maybe pulled away and removed from the anchoring member, as shown in theconfiguration 2470. The separation of the coupling mechanism occurs whenthe fusion member has been properly positioned and after the polymer isinjected (as further described by reference to FIGS. 26-28).

As mentioned above, the delivery housing channel of some embodiments canbe circular and constant in diameter throughout the entire length of thechannel as described above in FIGS. 7A-7C. In some such embodiment, theflexibility of the anchoring member enables the anchoring member to beadvanced through the curved channel of the fusion member.

FIGS. 26-28 illustrate an example of the injection of PMMA, or otherbone cement or hardening polymer, through the anchoring members and intothe vertebral bodies. Any number of known techniques/procedures forinjecting PMMA into the anchoring member can be used. One such techniqueinvolves injecting or pumping PMMA into the anchoring member through useof a needle or syringe.

In this example, two anchoring members are inserted into the twochannels of a fusion member. One of ordinary skill will realize that thesame operations can be performed for the embodiments that use fouranchoring members through a fusion block with four channels as furtherdescribed in Section V.

In FIGS. 26A-26C provide different views of two anchoring members 2610that are fully advanced through the fusion member channels and into themarrow space of adjacent vertebral bodies 2620 immediately above andbelow the fusion member 120. Polymer can be injected through the centrallumen of the anchoring members and out of the perforations of theanchoring members into the immediate surrounding area within the marrowspace of the penetrated vertebrae. FIGS. 27A-27B depict different viewsof the coalescence of the polymer collections 2710-2720 that resultfollowing injections of these polymers via anchoring members 2610,respectively. The coalescence 2710-2720 of these polymers forms aspherical or ellipsoidal “cloud” contiguous with the tip 2730-2740 ofthe anchoring members 2610. In its initial state, the polymer is in asemi-fluid state or in a gel-like state that allows it to flow throughthe anchoring member channel and the openings of its tip to fill in themarrow space of the vertebral body and the contours of the anchoringmember tip. However, within a short period of time, the polymer hardenswithin the marrow space, resulting in a structural union betweenanchoring members 2610, vertebral bodies 2620, and the fusion member120. The contoured tips of the anchoring members in conjunction with thehardened polymer prevent withdrawal of the anchoring member 2610 fromthe trabecular bone and enhances the structural integrity of the fusionmember 120. The final result is an intervertebral fusion member 120anchored via multiple anchoring members 2610 to collections of hardenedpolymer 2710-2720 (e.g., PMMA or other bone cement) and to thetrabecular bone of adjacent vertebral bodies 2620 yielding solidmechanical fusion. Once the anchoring members are in place, and thepolymer has been injected into the marrow space of the vertebral bodies,the driving members may be disengaged from the anchoring members andremoved from the patient.

Some embodiments insert more than one fusion member between a pair ofadjacent vertebral bodies. One such example is illustrated in FIGS.28A-28B. These figures depict (1) placement of two fusion members2810-2820 within the right and left paramedian disc space of vertebralbodies 2870-2880, (2) multiple sets of anchoring members into thevertebral bodies 2870-2880, and (3) coalescence of polymer “clouds”2830-2860 following the polymer injections. The resultant polymer cloudsfrom adjacent tips of anchoring members may form upon polymerization.The clouds along with multiple contoured and perforated anchoringmembers lock the fusion members 2810-2820 to the trabecular bone ofvertebral bodies 2870-2880.

3. Anchoring Member

As mentioned above in reference to FIG. 18, the anchoring member can becomposed of a material or a combination of materials that providesflexibility as shown in. To provide flexibility, the anchoring membercan be composed of materials such as nitinol, stainless steel, titaniumor other metals, metallic alloys, or high density polymers, carbonfiber, collagen or other biological materials, completely absorbable orpartially absorbable material, or of a combination of these materials.In some embodiments, the tip of the anchoring member may be open orclosed.

In some embodiments, the anchoring member can be composed of abio-absorbable polymer (such as collagen). Bio-absorbable polymer (e.g.,collagen) allows the anchoring member to be resorbed by the patient(e.g., three to four months in the case of collagen) after the anchoringmember has been inserted into the vertebral body of the patient. Somesuch bio-absorbable material (like collagen) also provides flexibilityto allow the anchoring member to have a range of motion from 0 to 90degrees. In some embodiments, the shaft of the anchoring member can becomposed of bio-absorbable material (e.g., collagen) while the tip ofthe anchoring member can be composed of another material (e.g., nitinol)to facilitate penetration of the anchoring member into the vertebralbody.

D. Fusion Apparatus

In some embodiments, the intervertebral fusion apparatus that includesthe anchoring member, fusion member, and delivery member is alreadypre-assembled. In some embodiments, the delivery housing and theretention rods are assembled to form the delivery mechanism. The fusionmember is coupled to the delivery mechanism by the retention rods. Theanchoring member is coupled to the driving member to form the anchoringmechanism.

However, in different embodiments, the fusion apparatus may bepre-assembled to different degrees. For instance, in some embodiments,the anchoring mechanism may be pre-assembled to varying degrees inrelation to the fusion member and the delivery mechanism. In someembodiments, the tip of the anchoring member of the anchoring mechanismis partially inserted in the fusion member channel. In otherembodiments, the tip of the anchoring member is inserted into thechannel of the delivery housing but not in the fusion member channel.Yet, in other embodiments, the anchoring mechanism is not inserted atall in the fusion member channel or in the delivery housing channel andmay be inserted into the apparatus when needed.

IV. Example of a Fusion Procedure

The operation of apparatus 110 will now be described. FIG. 29 depicts amedical procedure 2905 that involves the insertion of the apparatus 110of some embodiments of the invention. In this procedure, a medicalpractitioner (e.g., a physician) initially performs (at 2910) a partialor complete discectomy, which typically involves making an incision in apatient and removing some or all of the fibrocartilaginous disc betweentwo adjacent vertebral bodies. Any number of known techniques/procedurescan be used to remove the disc at 2910.

Next, the medical practitioner inserts the intervertebral fusion device(at 2915) and positions (at 2915) the fusion member (e.g., one of theblocks described above) between the endplates of adjacent vertebrae. Anynumber of known techniques/procedures for inserting a fusion memberbetween two adjacent vertebrae can be used (at 2915) to insert theintervertebral fusion device and position the interbody fusion memberbetween adjacent vertebrae. One technique for inserting the fusionmember involves the use of one of the delivery mechanisms (e.g.,apparatus 110 described above). In some embodiments, a radiograph orx-ray of the patient may be taken (at 2915) to determine if the fusionmember is placed at an appropriate position between two vertebralbodies. If not, the medical practitioner can use (at 2915) the deliverymechanism to reposition the fusion member to the desired location.

Once the fusion member has been properly positioned, the medicalpractitioner passes (at 2920) at least one anchoring member (e.g., largegauge needle) through the fusion member channels (at 2915) and advancesthe anchoring member into the marrow space of the adjacent vertebralbody by applying force on the proximal end of the driving member. Insome embodiments, a flange at the base of each anchoring member fitsinto a recess of increased diameter where the tubular channel meets theexposed surface of the fusion member, in order to lock the anchoringmember's position, anchoring it to the fusion member, as describedabove.

In some embodiments, the medical practitioner exerts force on thedriving member by tapping, hammering, or simply pushing at its proximalend to advance the anchoring member into the vertebral body, which theanchoring member encounters as it exits the fusion member channel inwhich it is inserted. To facilitate this penetration, the medicalpractitioner in some embodiments inserts a smaller gauge anchoringmember into the channel of the fusion member and into the marrow spaceof the adjacent vertebral body before inserting the anchoring member at2920. This creates a guide to help ensure the anchoring member will beadvanced into the proper position within the trabecular bone of thevertebral body. In some embodiments, a radiograph may be taken of theanchoring members in relation to the marrow space of the vertebralbodies to determine if the anchoring members need to be repositioned. Inother embodiments, a robotic arm may be used to advance the anchoringmember into the vertebral body.

Once the anchoring member is in position, the medical practitioner (at2925) injects polymethyl methacrylate (PMMA), other bone cement, orpolymer through the central channels of the driving member, interveningmember (if any) and the anchoring member, through the anchoring member'sopenings/perforations, and into the marrow space of the vertebral body.Ideally, the injected material forms a spherical or ellipsoidal cloud ofpolymer material (e.g., PMMA) contiguous with the tip of the anchoringmember.

In some embodiments, multiple anchoring members coupled with the drivingmember(s) may be advanced through multiple channels of the deliveryhousing and the fusion member into the same vertebral body. PMMA orother bone cement or polymer may be injected through the central lumenof these additional anchoring members. Accordingly, after 2925, themedical practitioner determines (at 2930) whether additional anchoringmembers need to be inserted into the fusion member inserted (at 2920).If so, the medical practitioner inserts (at 2920) additional anchoringmember(s) through another channel of the fusion member, and injects (at2925) polymer material through the central lumen of the additionalanchoring member and through its openings/perforations into the marrowspace of vertebral body. The resultant polymer (PMMA) clouds fromadjacent tips of the anchoring member may unite to form a single largercloud upon polymerization, with multiple contoured and perforatedanchoring members locked to the fusion member and anchored to the solidPMMA and trabecular bone of the vertebral body. The final result is anintervertebral fusion member anchored via multiple contoured, perforatedanchoring members to collections of PMMA and to the trabecular bone ofadjacent vertebral bodies yielding solid mechanical fusion.

When a determination has been made that the insertion of additionalanchoring members is not necessary, the medical practitioner (at 2935)uncouples the driving member from the anchoring member and removes thedriving member from the delivery housing and from the patient. In someembodiments, robotic arms may be used to uncouple the driving memberfrom the anchoring member and remove the driving member from thedelivery housing.

Once the driving member has been removed from the patient and thedelivery housing is no longer needed, the medical practitioner uncouplesthe retention rods from the fusion member. In some embodiments, this isachieved by rotating the retention rods 180 degrees so that theretention teeth of the retention rods disengage (at 2940) from theretention grooves of the fusion member. Once uncoupled, the retentionrods may be separated from the fusion member, and the delivery housingalong with the retention rods may then be removed (at 2940) from thepatient. In some embodiments, robotic arms may be used to uncouple theretention rods from the fusion member and remove the retention rods fromthe delivery housing.

In some embodiments, more than one fusion member is inserted between twoadjacent vertebral bodies. Accordingly, the medical practitionerdetermines (at 2945) whether another fusion member needs to be insertedbetween the vertebral bodies between which the last fusion member wasinserted (at 2915). If so, the medical procedure is repeated from 2915to 2940. Also, in some embodiments, the medical procedure 2905 isperformed multiple times to replace multiple discs between multiplepairs of vertebral bodies.

V. Alternatives Shapes and Structures

A. Arc Shaped Fusion Member Channels Traversing in a ParallelCross-Sectional Plane

The shape and composition of the fusion members and the anchoringmembers are different in different embodiments of the invention. Forinstance, in some embodiments, the anchoring members and thefusion-member channels are in shape of an arc as depicted in FIGS.30-33. In these figures, one set of tubular fusion member channels 3020and 3030 follow concentric semi-circular arcs to reach the inferior faceof fusion member 3010. The second set of tubular fusion member channels3040 and 3050 follow concentric semi-circular arcs to reach the superiorface of the fusion member 3010. Each set of concentric arcs traversealong a cross-sectional plane that runs parallel to one of the fusionmember surfaces.

These channels can be traversed by semi-circular arc shaped anchoringmembers, as illustrated in FIGS. 32-33. Specifically, FIGS. 32-33 showpassage of anchoring members through these semicircular tubular channelswith anchoring members 3200 and 3210 passing into the marrow space ofthe vertebral body (not pictured) beneath the fusion member, andanchoring members 3220 and 3230 passing into the vertebral bodycontiguous with the superior face of the fusion member (not pictured).Semi-circular arc-shaped channels and anchoring members simplify theprocess of inserting anchoring members into the channels, given thesmall space in which the fusion member is inserted between the vertebralbodies and the difficulty in accessing the proximal openings of thefusion member within the confines of the operative field. The anchoringmembers 3200-3230 are flexible in some embodiments, while being rigid inother embodiments.

FIG. 34 provides a detailed view of an anchoring member tip 3400 of someof the arc-shaped embodiments. As shown in this figure, a central lumen3410 of the arc-shaped anchoring member of some embodiments is in directcommunication with perforations 3420 along the anchoring member shaft aswell as the “teeth” or retention ridges 3430. This allows the polymermaterial to be delivered to the area adjacent to and between the angledteeth or retention ridges 3430, such that these surface contours canengage the polymer materials when it hardens, locking the anchoringmember in position within the trabecular bone, thereby locking thefusion member to the vertebral body.

In FIGS. 35-37, an embodiment of the fusion member 3500 includes twocurved semicircular channels 3510 and 3520. This figure shows curvedanchoring members 3530 and 3540 fully advanced through these channelsand into the marrow spaces of the vertebral bodies (not pictured) belowand above the fusion member. In FIG. 37, a polymer has been injected toform “clouds” 3700 and 3710 adjacent to the perforated, contoured tipsof anchoring members 3530 and 3540 within the marrow spaces of theadjacent vertebral bodies (not pictured). In this series of figures,channels 3510 and 3520 traverse cross-sectional planes parallel to oneanother as well as the lateral fusion member surfaces.

B. Fusion Member Channels Traversing in Non-Parallel Cross-SectionalPlanes

One of ordinary skill in the art will realize that differentconfigurations of the fusion member channels can traverse in x-, y-, andz-directions. FIGS. 38-40 depict an alternate embodiment of the fusionmember 3800 with curved channels 3810 and 3820 and curved channels 3830and 3840 extending to inferior and superior faces of the fusion member,respectively. Channels 3820 and 3840 traverse cross-sectional planesparallel to one another, as do channels 3810 and 3830. Both sets ofchannels traverse planes that are not parallel with any fusion membersurface.

FIGS. 41-42 depict an alternate embodiment of a fusion member thatincludes straight uncurled channels 4120. These channels traversecross-sectional planes that are non-parallel with any surface of thefusion member, and additionally, traverse cross-sectional planes thatare non-parallel with each other. The distal openings of these oblique,nonparallel channels 4120 are located at or near the geometric centersof the inferior and superior faces of the fusion member. As shown inthese figures, the fusion member 4110 includes two channels 4120 thatare traversed by anchoring members 4130 and 4140, which are rectangularin cross-sectional profile to match the cross-sectional profile of thechannels. FIG. 43 provides a detailed view of the anchoring membersdepicting the direct communication of the central anchoring member lumen4300 with perforations 4310 along the anchoring member shaft as well asthe “teeth” or retention ridges 4320 and a beveled tip 4330. In FIGS.44-45, polymer has been injected and forms “clouds” 4400 and 4410contiguous with the perforated, contoured tips of anchoring members 4130and 4140 within the marrow spaces of adjacent vertebral bodies (notpictured).

FIGS. 46A, 46B, and 47 depict an alternate embodiment of the fusionmember. Specifically, these figures depict a fusion member 4600, whichis similar to the fusion member 120 of FIG. 4. Channels 4610 and 4620traverse in parallel cross-sectional planes with respect to each otherbut are non-parallel with respect to the faces of the fusion member.FIG. 46B illustrates that each of the channels 4610 and 4620 tracecircular arcs that are a portion of two conceptual circles whichtraverse planes that are parallel to each other and non-parallel to allfaces of the fusion member. These channels are traversed by curvedanchoring members (not pictured). Although this embodiment provides forchannels and anchoring members that trace the arcs of conceptualcircles, other embodiments provide for alternative curved conceptualshapes (e.g. ellipses, parabolas, etc.). The distal openings of thechannels 4610 and 4620 may be located at or near the geometric centersof the inferior and superior faces of the fusion member.

C. Alternative Anchoring Member Tips and Structures

As shown above, different embodiments use different shapes for theanchoring members (e.g., arc-shape, angled-shape, semi-circular shape,straight, etc.). Different embodiments also use different types ofanchoring members. FIGS. 48A-48B provide a detailed view of alternativeembodiments 4801, 4802, and 4803 of anchoring member tips. As shown inthe figures, the central lumen 4800-4810 of the anchoring members are indirect communication with perforations 4815, 4820, and 4825 along theanchoring member shaft as well as the “teeth”, or retention ridges,4830, 4835, and 4840. FIG. 48B illustrates that in some embodiments, theanchoring members have beveled tips 4804.

In some embodiments, the maximum diameter or circumference of thesegment of the anchoring member that includes retention ridges or othersurface features intended to engage the polymer material (e.g., PMMA orbone cement) is less than or equal to the diameter or circumference ofproximal and distal anchoring member segments. This allows the anchoringmember to be hammered, tapped, or simply pushed into position within themarrow space of the vertebral bodies rather than being screwed intoplace.

FIGS. 48C-48D illustrate that the anchoring members of some embodimentshave threads. As shown, the threads may run the entire length of theanchoring member, from the base of the anchoring member to the tip ofthe anchoring member. In other embodiments (not shown), the threads runthrough only a segment of the anchoring member (i.e., less than theentire length of the anchoring member). The threads allow the anchoringmembers to be screwed into the desired position within the marrow spaceof the vertebral bodies. In some embodiments, the fusion member channelsinto which the anchoring members are advanced include grooves thatcompliment the threads of the anchoring members.

D. Fusion Members with Ridges and Additional Bone-Grafting Channels

FIG. 49 depicts various fusion member surface contour features includingorthogonal ridges 4900, angled ridges 4910, and oblique parallel ridges4920. Longitudinal channels 4930 and 4940 and transverse channels 4950and 4960 for positioning and retention of bone graft material are alsoillustrated. These surface contours and retention channels may becombined with any of the fusion member channel configurations previouslydescribed. Bone grafting channels may be of any size and position andallow for the positioning of bone grafting material between and incontact with the opposed endplates of the adjacent vertebral bodies aswell as extending from one lateral face to another lateral face of thefusion member. Placement of the bone graft material in the disc spacesurrounding the fusion member permits the progressive solid bony fusionbetween the fusion member and the adjacent vertebral bodies.

E. Retention Teeth and Retention Grooves of Variable Dimensions

In some embodiments, retention teeth and retention grooves are ofvariable width and height. FIGS. 50 and 51 illustrate a retention rod5005 with retention teeth (only one tooth 5010 is shown) that engagewith a set of larger diameter retention grooves 5120 of a retentiongroove set 5110 of a fusion member 5100. In FIG. 50, the retention tooth5010 includes a directional decrease in tooth height and a directionaldecrease in tooth width when traversing the contour of the tooth in theindicated direction of rotation. The width 5020 of the retention tooth'sleading edge is less than the width 5030 of the retention tooth'strailing edge. The height 5040 of the retention tooth's leading edge isless than the height 5050 of the retention tooth's trailing edge. Theretention tooth tapers in two directions. Specifically the retentiontooth (1) tapers in the radial direction (i.e. height), and (2) tapersin the lateral direction (i.e. width) when traversing the circumferenceof the tooth.

In FIG. 51, the set of larger diameter retention grooves 5120 of theretention groove set 5110 also decreases in height and width whentraversing the contour of the groove in the indicated direction ofengagement to match the profile of the retention tooth 5010.Specifically, the retention tooth 5010 is inserted first into opening5130, which exhibits greater height and width compared to opening 5140.When the tooth's leading edge with smaller dimensions is fully engagedwith the opening 5140 with smaller dimensions and the tooth's trailingedge with larger dimensions is fully engaged with the opening 5130 withlarger dimensions, the retention rod can no longer be rotated. Thetooth's flared shape and matching flared profile of the larger-diameterretention grooves 5120 of the retention groove set 5110 prevent theretention rod from being withdrawn laterally from the fusion member5100. When decoupling the retention rod from the fusion member 5100, theretention tooth's trailing edge with smaller dimensions is the last toclear the larger diameter retention grooves, facilitating clearance andremoval of the retention rod.

F. Various Configurations of Fusion Members and Anchoring Members

As mentioned above, some embodiments of the invention provide a fusionmember with four channels and four anchoring members that are advancedinto these fusion member channels as shown in FIG. 52.

FIGS. 53-55 illustrate an example of the injection of PMMA, or otherbone cement or hardening polymer, through the anchoring members and intothe vertebral bodies. In this example, four anchoring members areinserted into the four channels of a fusion block. One of ordinary skillwill realize that the same operations can be performed for theembodiments that use two anchoring members through a fusion block withtwo channels.

In FIG. 53, anchoring members 5310-5340 are fully advanced through thefusion member channels and into the marrow space of adjacent vertebralbodies 5360-5370 immediately above and below the fusion member 5350.Polymer can be injected through the central lumen of the anchoringmembers and out of the perforations of the anchoring members into theimmediate surrounding area within the marrow space of the penetratedvertebrae. FIG. 54 depicts the coalescence of the polymer collections5410-5420 that result following injections of these polymers viaanchoring members 5310-5340, respectively. The coalescence 5410-5420 ofthese polymers forms a spherical or ellipsoidal “cloud” contiguous withthe tip of the anchoring members 5310-5340. The polymer hardens withinthe marrow space, resulting in a structural union between anchoringmembers 5310-5340 in addition to anchoring each vertebral body 5360-5370to the fusion member 5350. The contoured tips of the anchoring membersin conjunction with the hardened polymer prevent withdrawal of theanchoring members 5310-5340 from the trabecular bone and enhances thestructural integrity of the fusion member 5350. The final result is anintervertebral fusion member 5350 anchored via multiple anchoringmembers 5310-5340 to collections of hardened polymer (e.g., PMMA orother bone cement) and to the trabecular bone of adjacent vertebralbodies 5360-5370 yielding solid mechanical fusion. Once the anchoringmembers 5310-5340 are in place, and the polymer has been injected intothe marrow space of the vertebral bodies, the driving members may bedisengaged from the anchoring members and removed from the patient.

Some embodiments insert more than one fusion member between a pair ofadjacent vertebral bodies. One such example is illustrated in FIG. 55.This figure depicts placement of two fusion members 5510-5520 within theright and left paramedian disc space of vertebral bodies 5570-5580,multiple sets of anchoring members advanced into the vertebral bodies5570-5580, and coalescence of polymer “clouds” 5530-5560 following thepolymer injections. The resultant polymer clouds from adjacent tips ofanchoring members may unite to form a single larger cloud uponpolymerization. The united cloud along with multiple contoured andperforated anchoring members locks the fusion members 5510-5520 to thetrabecular bone of vertebral bodies 5570-5580.

VI. Embodiments that do not Use Polymer Materials

While the invention has been described with reference to numerousspecific details, one of ordinary skill in the art will recognize thatthe invention can be embodied in other specific forms without departingfrom the spirit of the invention. In some embodiments, the anchoringmembers may be without a central lumen or perforations along theirshaft. In some embodiments, angled teeth, back-facing ridges, and othersurface retention ridges may be greater in circumference or diameterthan the more proximal or distal anchoring member segments. In theseinstances, after the anchoring members are advanced into the marrowspace of the vertebral bodies, injection of polymer materials may not beneeded to anchor the vertebral bodies to the fusion member. The surfacecontours of the anchoring members will anchor the vertebral bodies tothe fusion member.

Also, in several of the above-described embodiments, the channels andanchoring members have circular-arc cross-sectional profiles. However,in other embodiments, the channels and anchoring members havealternative curved arc shapes.

I claim:
 1. A medical procedure comprising: removing a disc between twovertebral bodies of a patient; delivering a fusion member between thetwo vertebral bodies using a retention mechanism, the fusion membercomprising a first set of coupling members, the retention mechanismconfigured to hold the fusion member while delivering the fusion memberbetween the two vertebral bodies, the retention mechanism comprising asecond set of coupling members configured to controllably couple withthe first set of coupling members in order to controllably hold thefusion member, wherein the first set of coupling members comprises aplurality of indentations, the second set of coupling members comprisesa plurality of teeth configured to rotatably couple with the pluralityof indentations and the width of each tooth increases along thedirection of height of the tooth and the width of the indentationcoupled to said tooth matches the width of the tooth.
 2. The medicalprocedure of claim 1 further comprising coupling the retention mechanismto the fusion member.
 3. The medical procedure of claim 2, wherein thecoupling comprises rotatably coupling the first and second sets ofcoupling members.
 4. The medical procedure of claim 1 further comprisingdetermining whether the fusion member is in a desired position betweenthe vertebral bodies.
 5. The medical procedure of claim 4, wherein thedetermining comprises taking an intra-operative image of the patient. 6.The medical procedure of claim 4 further comprising: when the fusionmember is in the desired position, decoupling the retention mechanismfrom the fusion member to remove the retention mechanism from thepatient.
 7. The medical procedure of claim 1, wherein the second set ofcoupling members is further configured to controllably decouple from thefirst set of coupling members in order to controllably release thefusion member.
 8. The medical procedure of claim 1, wherein one of thefirst and second sets of coupling members comprises a set of malecoupling members while the other set comprises a set of female couplingmembers.
 9. A medical procedure comprising: removing a disc between twovertebral bodies of a patient; delivering a fusion member between thetwo vertebral bodies using at least one retention rod, the fusion membercomprising a first set of coupling members, the retention rod comprisinga second set of coupling members that is configured to couple with thefirst set of coupling members, wherein the first set of coupling memberscomprises a plurality of indentations, the second set of couplingmembers comprises a plurality of teeth configured to rotatably couplewith the plurality of indentations and the width of each tooth increasesalong the direction of height of the tooth and the width of theindentation coupled to said tooth matches the width of the tooth. 10.The medical procedure of claim 9 further comprising coupling theretention rod to the fusion member.
 11. The medical procedure of claim10, wherein the retention rod further comprises (i) a shaft on which thesecond set of coupling members is located and (ii) a handle coupled tothe shaft; wherein the handle is for allowing the rotation of the shaftin a particular direction to decouple the second set of coupling membersfrom the first set of coupling members of the fusion member; whereinsaid decoupling allows the retention rod to be retracted from thepatient while leaving the fusion member between the two vertebralbodies.
 12. The medical procedure of claim 9, wherein one of the firstand second sets of coupling members comprises a set of male couplingmembers while the other set comprises a set of female coupling members.13. The medical procedure of claim 9, wherein the width of eachindentation and the width of the tooth coupled to said indentation varyalong the direction of rotation of the shaft in order to ensure that thetooth and the indentation decouple in only one direction of rotation ofthe shaft.
 14. The medical procedure of claim 9, wherein the height ofeach indentation and the height of the tooth coupled to said indentationvary along the direction of rotation of the shaft in order to ensurethat the tooth and the indentation decouple in only one direction ofrotation of the shaft.
 15. The medical procedure of claim 9, whereineach tooth encompasses less than 180 degrees of the retention rod alonga direction of rotation of the retention rod.
 16. The medical procedureof 1, wherein each tooth encompasses less than 180 degrees of theretention rod along a direction of rotation of the retention rod.